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Inclusion Constraints over Nonempty Sets of Trees
, 1997
"... We present a new constraint system called INES. Its constraints are conjunctions of inclusions t1 `t2 between firstorder terms (without set operators) which are interpreted over nonempty sets of trees. The existing systems of set constraints can express INES constraints only if they include ne ..."
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Cited by 14 (5 self)
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We present a new constraint system called INES. Its constraints are conjunctions of inclusions t1 `t2 between firstorder terms (without set operators) which are interpreted over nonempty sets of trees. The existing systems of set constraints can express INES constraints only if they include negation. Their satisfiability problem is NEXPTIMEcomplete. We present an incremental algorithm that solves the satisfiability problem of INES constraints in cubic time. We intend to apply INES constraints for type analysis for a concurrent constraint programming language.
Ordering Constraints over Feature Trees
, 1999
"... Feature trees are the formal basis for algorithms manipulating record like structures in constraint programming, computational linguistics and in concrete applications like software configuration management. Feature trees model records, and constraints over feature trees yield extensible and modular ..."
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Cited by 13 (5 self)
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Feature trees are the formal basis for algorithms manipulating record like structures in constraint programming, computational linguistics and in concrete applications like software configuration management. Feature trees model records, and constraints over feature trees yield extensible and modular record descriptions. We introduce the constraint system FT of ordering constraints interpreted over feature trees. Under the view that feature trees represent symbolic information, the relation corresponds to the information ordering ("carries less information than"). We present two algorithms in cubic time, one for the satisfiability problem and one for the entailment problem of FT . We show that FT has the independence property. We are thus able to handle negative conjuncts via entailment and obtain a cubic algorithm that decides the satisfiability of conjunctions of positive and negated ordering constraints over feature trees. Furthermore, we reduce the satisfiability problem of Dorre's weak subsumption constraints to the satisfiability problem of FT and improve the complexity bound for solving weak subsumption constraints from O(n^5) to O(n³).
Feature Trees over Arbitrary Structures
 Specifying Syntactic Structures, chapter 7
, 1997
"... This paper presents a family of first order feature tree theories, indexed by the theory of the feature labels used to build the trees. A given feature label theory, which is required to carry an appropriate notion of sets, is conservatively extended to a theory of feature trees with the predicat ..."
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Cited by 10 (2 self)
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This paper presents a family of first order feature tree theories, indexed by the theory of the feature labels used to build the trees. A given feature label theory, which is required to carry an appropriate notion of sets, is conservatively extended to a theory of feature trees with the predicates x[t]y (feature t leads from the root of tree x to the tree y), where we have to require t to be a ground term, and xt# (feature t is defined at the root of tree x). In the latter case, t might be a variable. Together with the notion of sets provided by the feature label theory, this yields a firstclass status of arities.
Weak Subsumption Constraints for Type Diagnosis: An Incremental Algorithm
 In Joint COMPULOGNET /ELSNET/EAGLES Workshop on Computational Logic for Natural Language Processing
, 1995
"... We introduce constraints necessary for type checking a higherorder concurrent constraint language, and solve them with an incremental algorithm. Our constraint system extends rational unification by constraints x⊆y saying that “x has at least the structure of y”, modelled by a weak instance relatio ..."
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Cited by 1 (1 self)
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We introduce constraints necessary for type checking a higherorder concurrent constraint language, and solve them with an incremental algorithm. Our constraint system extends rational unification by constraints x⊆y saying that “x has at least the structure of y”, modelled by a weak instance relation between trees. This notion of instance has been carefully chosen to be weaker than the usual one which renders semiunification undecidable. Semiunification has more than once served to link unification problems arising from type inference and those considered in computational linguistics. Just as polymorphic recursion corresponds to subsumption through the semiunification problem, our type constraint problem corresponds to weak subsumption of feature graphs in linguistics. The decidability problem for weak subsumption for feature graphs has been settled by Dörre [Dör94]. In contrast to Dörre’s, our algorithm is fully incremental and does not refer to finite state automata. Our algorithm also is a lot more flexible. It allows a number of extensions (records, sorts, disjunctive types, type declarations, and others) which make it suitable for type inference of a fullfledged programming language.
A Type is a Type is a Type
 DRAFT RESEARCH REPORT, DFKI, STUHLSATZENHAUSWEG 3, D66123 SAARBRUCKEN
, 1995
"... We present an incremental constraint solver as the nucleus of a soft type checker for a higherorder concurrent constraint language. Designed as a ..."
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We present an incremental constraint solver as the nucleus of a soft type checker for a higherorder concurrent constraint language. Designed as a